The present invention relates to a device for cleaning air ports of a furnace, especially a furnace of a chemical recovery boiler.
Black liquor obtained during the production of pulp is combusted in a soda recovery boiler for recovering chemicals and producing energy. The burning of organic material contained in the black liquor requires an abundant amount of air to ensure as complete combustion as possible and maintain a high process efficiency. Air is fed into the furnace of the boiler through air ports located in the wall of the furnace. The ports are conventionally laid out in horizontal rows located at several elevations up the furnace. The ports in the wall are usually provided with nozzles which direct the air into the furnace. The air is fed into the air ports from air ducts surrounding the furnace via wind boxes or the like. Usually, the air is introduced into the furnace through at least three elevational levels of the furnace. Air ports in the furnace wall are generally provided at each level. Typically, the lowest air port level is a primary air level, the middle air port level is a secondary air level, and the uppermost air port level is a tertiary air level. Nozzles for injecting the liquid liquor may be arranged between the secondary and tertiary air port level. More than three air port levels for introducing air into the furnace may be arranged in the boiler.
Liquor and other liquid or slurry solutions flow from the walls of the boiler to the edge of the air ports on the side of the furnace. On the inside surface of the furnace walls, the solutions solidify and tend to plug the air ports. The airflow being fed via the ports into the furnace is not capable alone of keeping the ports clear of these deposits. The air ports must frequently be freed of any built-up excrescent material by rodding, a known cleaning technique to repeatedly insert a cleaning rod (or rodder) into the air port to dislodge the build up of material and thereby ensure adequate airflow into the boiler. Rodding can be either manual or automatic.
Some air port cleaning devices are provided with a cleaning head, which reciprocates in and out of the air ports during the cleaning. These cleaning heads remove slag, e.g., deposits, from the air ports. Adjacent to the air port there is a damping plate for regulating the volume of airflow being introduced into the furnace. The cleaning head can interfere with the operation of the damper. The cross-sectional area of the sleeve-like cleaning head is somewhat smaller than the cross-sectional area of the air nozzle. Usually, the cleaning head is connected with a rod to an actuator, such as a pneumatic or hydraulic cylinder. The actuator effects the reciprocating motion of the cleaning sleeve. The cylinder of the actuator is located outside the air register. The cylinder is connected to a long rod that extends through the air register to connect to the cleaning head. Usually, the damper of the register is moved to its extreme position during the use of the cleaning sleeve to avoid disturbing the motion of the rod of the cylinder. This repositioning of the damper during cleaning causes disturbances in the airflow pattern flowing into the air port and further into the furnace, and results in undesirable boiler operation.
There is a long-felt need in the field of furnaces, especially those in chemical recovery boilers, to provide a cleaning device for air ports that eliminates or reduces the problems discussed above. It would be beneficial to have a cleaning device that efficiently removes deposits from an air port without interfering with the on-going airflow into the furnace. It would also be beneficial for the cleaning device to have an open construction to allow air to cool the cleaning device and air register adjacent to the air port. The cleaning device is further preferably devoid of elements that might disturb the airflow through the register, air port and into the furnace.
A sleeve-like or annular cleaning head has been developed which reciprocally slides into an air port and fits into a lower section of an air register. The cleaning device has a cleaning head with a cross-sectional shape that is similar to the cross-sectional shape of an air port. The cleaning head is attached to an elongated head support having a cross-sectional shape similar to a lower portion of the air register. The cleaning head is adapted to slide back and forth into the air port, and thereby dislodge debris from the port. Actuating members are operationally connected to an opposite end of the head support for reciprocally moving the cleaning head in the air port. The walls of the cleaning head and head support are provided with holes to allow air to flow through and cool the walls of the cleaning device.
In one embodiment, the invention is a cleaning device for cleaning an air port in a wall of a furnace having an air register adjacent to an air port in an outside of the wall of the furnace. The cleaning device comprises: a cleaning head having a substantially-open, cross-sectional shape conforming to a cross-sectional shape of the air port, said clean head moving reciprocally in and out of the air port, and a head support extending from the cleaning head, through the air register and attached to an actuator, said actuator reciprocally moving the head support, and said head support having perforated walls permitting air to flow through the walls.
The cleaning device is especially suitable for cleaning secondary and tertiary air ports of a furnace in a recovery boiler. It may also be used for cleaning other air ports, especially in the upper part of a furnace. The cleaning device is especially suitable for use with air registers, wherein the flow direction of the air changes essentially as the air arrives from a wind box or the like into the air register. As the air enters and passes through an air register, the flow turns typically 90xc2x0 (xc2x120xc2x0) in relation to its inflow direction.